I´m doing a parasitic draw test on my car battery, in order to check the draw with the car locked and alarmed I need to use the COM and 20a sockets of the Multimeter, if I use the COM and mA sockets the battery doesnt make a circuit (car dead). Whats the mA reading on the Multimeter, 240 mA??
Most likely here is what is happening.
The fuse for the mA circuit in your meter is blown and that is why it is not making a connection with the red lead in the mA plug.
With the lead of the meter in the 20A plug, only when the dial is set to A do you get a valid reading. With the red lead in the 20A plug and the dial set to mA the reading that you see is just noise, not a valid reading.